Youth are not meeting PA (physical activity) guidelines, which increases their risk of obesity and related diseases such as type 2 diabetes. Therefore, it is crucial to identify methods to encourage youth to be more physically active. Virtual reality has been successfully proven to be effective at promoting desired behaviors. Youth enjoy video games, and players appear to identify with avatars, particularly those that are self-representative. Thus, design of youth-oriented immersive games where the player's live body actions can control the fate of the avatar in a virtual world may provide a promising method for increasing PA among this group at risk for low levels of PA. The research proposed in this application represents an early step in this line of research. It will create an immersive, interactive virtual reality game where the player's movements influence the fate of the avatar. Specifically, this research will work with youth to develop an immersive virtual reality game to be played via natural human computer interfaces, develop a system for creating highly self- representational avatars, develop an algorithm to unobtrusively measure PA during game-play, and conduct a pilot study to assess the feasibility of these components. If proven to be feasible, this research will provide the basis for an R01 application to assess the efficacy of this approach at increasing PA among a large number of youth in various real-world settings.